26 



BULLETIN 746, U. S. DEPARTMENT OF AGRICULTURE. 



Table V. — Relationship of mean temperature to developmental period in larva 

 stage of the sugar-cane moth borer — Continued. 



Mean tem- 



Average 



Number 



Mean tem- 



Average 



Number 



perature. 



period . 



of records. 



perature. 



period. 



of records. 



"F. 



Days. 





°F. 



Days. 





70 



45 



1 



81 



45 



2 



.70.6 



39 



1 



81.5 



35.1 



7 



70.8 



34 



1 



81.7 



46 



1 



71.4 



33 



1 



82 



50 



2 



71.7 



35 



1 



82.1 



65 



1 



71.9 



37 



1 



82.2 



54.5 



2 



72 



38 



2 



82.4 



52 



1 



72.1 



38.5 



2 



82.5 



57.6 



3 



72.2 



22 



1 



82.6 



42.5 







72.3 



37 



2 



82.7 



40.4 



5 



72.9 



24 



1 



82.8 



36 



12 



73.3 



25.8 



5 



82.9 



31.1 



19 



73.5 



27 



1 



83 



24.3 



6 



73.9 



28 



1 



83.1 



31 



1 



74 



39 



1 



83.3 



71 



1 



74.4 



49 



2 



83.4 



34 



1 



75.1 



54 



2 



83.7 



34 



2 



75.4 



33 



1 



83.8 



32.8 



7 



76.1 



60.3 



2 



83.9 



38.8 



10 



76.2 



66 



2 



84 



24 



3 



76.3 



26 



1 



84.1 



45.5 



4 



76.5 



27 



1 



84.2 



29.7 



8 



76.8 



28 



1 



84.3 



38.5 



2 



77.1 



32 



2 



84.4 



29.6 



9 



77.2 



38 



2 



84.5 



20.5 



9 



77.5 



31 



1 



84.6 



25.5 



5 



78 



34 



1 



84.8 



25.5 



2 



78.1 



71 



1 



84.9 



26.2 



13 



78.2 



28 



3 



85 



25 



8 



78.3 



48 



1 



85.1 



19 



1 



78.5 



22 



1 



85.4 



54 



1 



PUPAL CELLS. 



When the larvse are fully grown they construct a kind of pupal 

 cell before pupating. The larval tunnel is cleaned, enlarged, and 

 extended to the rind of the cane, where a small circular opening 4 to 

 5 mm. in diameter is made. The rind is not completely cut out, 

 but it is eaten away from the inside until only a thin paperlike 

 section, lightly attached at the edges, remains. This is held in place 

 by threads of silk fastened to the inside so that the moth can easily 

 escape, but other insects can not enter. The lower end of the cell 

 is closed with frass and silk, and the whole cell is lightly lined with 

 silk. In the rearing tubes in the insectary the pupal cell usually is 

 formed on the side of the cane between it and the sides of the class. 



As the pupal cell nears completion the larva merges into the pre- 

 pupa stage. No molt occurs, but the larva ceases feeding and 

 becomes sluggish and helpless. The body contracts longitudinally, 

 especially the thorax, while the use of the legs is lost and the insect 

 thrashes about as do the pupae. From 1 to 3 days are spent in the 

 prepupa stage, but it often happens that this stage is not noticed by 

 an observer, as it is not very distinct from the larva stage. 



PUPATION. 



After resting for a short time as a prepupa the pupa is disclosed 

 by the casting of the last larval skin in the same manner as the 

 others are cast. 



